The minimum number of years used to calculate these Normals is indicated by a
code for
each element.
A "+" beside an extreme date indicates that this date is the first occurrence
of the extreme value. Values and dates in bold indicate all-time extremes for
the location.

Data used in the calculation of these Normals may be subject to further quality
assurance checks. This may result in minor changes to some values presented here.

Probability of last temperature in spring of 0 °C or lower on or after indicated dates

10%

25%

33%

50%

66%

75%

90%

Date

May 27

May 18

May 17

May 12

May 08

May 06

Apr 30

Probability of first temperature in fall of 0 °C or lower on or after indicated dates

10%

25%

33%

50%

66%

75%

90%

Date

Sep 19

Sep 23

Sep 24

Sep 28

Oct 05

Oct 07

Oct 11

Probability of frost-free period equal to or less than indicated period (Days)

10%

25%

33%

50%

66%

75%

90%

Days

119

132

135

139

144

147

155

Legend

A = WMO "3 and 5 rule" (i.e. no more than 3 consecutive and no more than 5 total missing for either temperature
or precipitation)

B = At least 25 years

C = At least 20 years

D = At least 15 years

Statistics listed below are provided as a guide to determine the
validity of Normals and Extremes calculations.
For example, a station with 30 years of record between 1981 and
2010 with no missing years would be a more reliable normal than
a station with 15 years of record and 2 missing years.
Less than 100% possible observations indicates that out of
the total number of observations used, some records were
missing.

"Climate averages", "climate means" or "climate normals"
are all interchangeable terms. They refer to arithmetic calculations
based on observed climate values for a given location over a specified
time period. Climate normals are often used to classify a region's
climate and make decisions for a wide variety of purposes involving
basic habitability, agriculture and natural vegetation, energy use,
transportation, tourism, and research in many environmental fields.
Normals are also used as a reference for seasonal monitoring of
climate temperature and precipitation for basic public interest, and
for monitoring drought or forest fires risk. Real-time values, such as
daily temperature, are often compared to a location's "climate normal"
to determine how unusual or how great the departure from "average"
they are.

The World Meteorological Organization (WMO) recommends that countries prepare
climate normals for the official 30-year normals periods ending in 1930, 1960
and 1990, for which the WMO World Climate Normals are published. In addition,
WMO recommends the updating of climate normals at the
end of every decade as provided here for 1981 to 2010.

Calculation Method

Calculation Method

There are many ways to calculate "climate normals"; the most useful ones adhere to accepted standards. The WMO considers
thirty years long enough to eliminate year-to-year variations. Thus the WMO climatological standard period for normals
calculations are computed over a 30 year period of consecutive records, starting January 1st
and ending December 31st. In addition, the WMO established
that normals should be arithmetic means calculated for each month of
the year from daily data with a limited number of allowable missing
values. For normals values representing averages, such as temperature,
a month was not used if more than 3 consecutive days or more than a
total of 5 days were missing. This rule is referred to as the "3 and 5
rule" established as a guideline for completeness by the WMO.
Furthermore, its corresponding year-month mean should not be computed
and should be considered missing. For normals values representing
totals, such as precipitation, degree-days, or days with, an
individual month was required to be 100% complete in order for it to
be included in the normals calculation.

First, the average or total, as appropriate for the element, for all individual months was calculated for all locations.
Normals values were then calculated as the mean for each month from all the individual months in the period that sufficiently
fulfilled the requirement for completeness for 1981 to 2010. With the exception of the annual standard deviation (see
calculations below), the annual normal value was calculated as the mean or total of monthly normals values only for stations
where means or totals for every month of the year were available.

APPENDIX A lists the specific type of
calculation, applicable period, and completeness requirements for each
normals and extremes element.

Normals Code

Once the qualifying months were determined, the "3/5" rule was also applied to the number of months used to calculate
average mean or average total within the thirty-year period. For instance, the "normal" value of a monthly element, such
as normal maximum temperature for May, can have no more than 3 consecutive or 5 total missing months of May between
1981 to 2010.

A normal code was assigned for each month according to the
completeness criteria presented in Table 1. With the exception of the
annual standard deviation calculated for mean temperature, the monthly
code that represented the least degree of completeness was assigned to
the annual normal code for that element and location.

WMO "3 and 5 rule" (i.e. no more than 3 consecutive and no more than 5 total missing for both
temperature and precipitation).

A

WMO "3 and 5 rule" (i.e. no more than 3 consecutive and no more than 5 total missing for either
temperature or precipitation).

B

At least 25 years

C

At least 20 years

D

At least 15 years

E

At least 10 years

F

At least 5 years

G

< 5 years

Note that stations with a normal code of "A" in both temperature and
precipitation are designated as meeting the WMO standard for normals
calculation.

While normals for all available elements for all stations were
calculated, only elements with a normals code of at least Class D, or
15 years are currently available through the Archive Online website.

Uncertainty due to shorter period

Uncertainty due to shorter period

Apart from any uncertainty due to site, instrument, or observing
program changes, or general representativeness of the observing site
with the surrounding region, the normals for most locations will have
some uncertainty due to the fact that the observations are not
complete for the 30-year period.

Standard Deviation Calculations

Standard Deviation Calculations

Standard deviations of mean daily temperatures (°C)
are calculated from the same data used to calculate the mean for each month.
Calculation of annual standard deviation differs from other annual element
calculations in that it represents the mean standard deviation calculated
from annual means for a given station rather than the mean standard deviation
of monthly means. The same "3 and 5" rule for data completeness was applied
to the annual standard deviation as was applied to
the individual monthly standard deviations. The normal code for
the annual standard deviation was assigned according to the
qualifications outlined in Table 1 rather than
representing the least degree of completeness for all months.

Climate Extremes

Climate Extremes

Besides the monthly averages and totals, extremes for selected elements by
month including the daily maximum and minimum temperature, and the daily
rainfall, snowfall, and total precipitation, and the dates of occurrence,
were compiled and provided along with the normals elements. Extremes are
compiled from the entire period of record of each location and not restricted
to just the 1981-2010 normals period.
In each case, the first or oldest date of occurrence is recorded below the
extreme value. Values which occur more than once are identified with a (+).
Bolded values and dates indicate the extreme
for the year. Because no completeness requirements apply, no normals
codes are assigned to extreme elements.

Support Information

Support Information

During the calculation of normals and extremes, additional support
information was tabulated. These include for both means and extremes:
total number of available years, number of missing years, total count
of observations and percent possible observations used. The first year
and last year used within the normals period for elements for which
means were calculated are available. The first year and last year used
for element for which extremes were determined are available.

Data Adjustments

Data Adjustments

No explicit corrections or adjustments were made to normals values
to account for any variations in siting, instruments, or observing
procedures. To the degree that these confounding influences can affect
trends in temperature and precipitation, these normals values should
not be used to draw precise conclusions about changes in climate.

All normal values are derived from data in the National
Climatological Archive of Environment Canada. While considerable
effort is made to ensure the accuracy of these data, no guarantee can
be given that they are error free.

Data and Observing Stations

Data and Observing Stations

The normals elements of greatest interest are the daily values of maximum, minimum
and mean temperature (°C), rainfall (mm),
snowfall (cm) and total precipitation (mm).
For principal stations, additional daily elements such as peak wind
gusts and elements based on hourly elements such as wind, sunshine, and solar
radiation are also available.
Generally the network of volunteer stations is limited to basic daily temperature
and precipitation observations.

The climate day at first order or primary observing sites is defined by the 24-hour
period ending at 0600 UTC. The climate at volunteer observing
sites ends at around 8:00 am local time and can vary somewhat from location to location.

As in many other countries, observing practices have evolved through the current
normals period, and continue to evolve. Observations at one time almost exclusively
taken and recorded by human observers are increasingly being automated. Some principal
stations in the MSC network were automated during the 1990's. As this occurred, the
only precipitation observations available were daily total precipitation (mm)
from an automatic weighing precipitation gauge. The observations from these stations
in these years (mostly the late 1990's) were not used for the normals calculations
since daily rainfall and snowfall observations were not available.

Temperature

Temperature

Temperature measurements are made from self-registering maximum and minimum thermometers
set in a louvered, wooden shelter.
The shelter is mounted on a stand so that the thermometers are approximately 1.5 m
above ground, which is usually a level, grassy surface.

At most climatological stations, maximum temperature is the highest
temperature recorded in a 24-hour period ending in the morning of the
next day. The minimum values are for a period of the same length,
beginning in the evening of the previous day. Mean temperature is the
average of the two.

At most principal stations, the climatological day begins at 0600 UTC (Universal Time Coordinate)
and ends at the onset of 0600 UTC on the following day. These times are equivalent or
close to midnight local standard time for most of Canada.

Rainfall, Snowfall, and Precipitation

Rainfall, Snowfall, and Precipitation

Rain, drizzle, freezing rain, freezing drizzle and hail are usually measured using
the standard Canadian rain gauge, a cylindrical container 40 cm
high and 11.3 cm in diameter.
The precipitation is funneled into a plastic graduate which serves as the measuring device.

Snowfall is the measured depth of newly fallen snow, measured using
a snow ruler. Measurements are made at several points which appear
representative of the immediate area, and then averaged.
"Precipitation" in the tables is the water equivalent of all types of
precipitation.

At most ordinary stations the water equivalent of snowfall is
computed by dividing the measured amount by ten. At principal stations
it is usually determined by melting the snow that falls into Nipher
gauges. These are precipitation gauges designed to minimize turbulence
around the orifice, and to be high enough above the ground to prevent
most blowing snow from entering. The amount of snow determined by this
method normally provides a more accurate estimate of precipitation
than using the "ten-to-one" rule. Even at ordinary climate stations
the normals precipitation values will not always be equal to rainfall
plus one tenth of the snowfall. Missing observations is one cause of
such discrepancies.

Precipitation measurements are usually made four times daily at
principal stations. At ordinary sites they are usually made once or
twice per day. Rainfall, snowfall and precipitation amounts given in
the tables represent the average accumulation for a given month or
year.

Snow Depth

Snow Depth

Snow cover is the depth of accumulated snow on the ground, measured
at several points which appear representative of the immediate area,
and then averaged. End-of-month values are given in the tables.

Number of Days With Specified Parameters

Number of Days With Specified Parameters

These elements give the average number of days per month or year on which
a specific meteorological event or parameter threshold occurs. In the case
of rainfall and precipitation, 0.2 mm or
more must occur before a "day with" is counted.
The corresponding figure for snowfall is 0.2 cm.

List of Days with parameters and thresholds

Days with Maximum Temperature

≤ 0 °C

> 0 °C

> 10 °C

> 20 °C

> 30 °C

> 35 °C

Days with Minimum Temperature

> 0 °C

≤ 2 °C

≤ 0 °C

< -2 °C

< -10 °C

< -20 °C

< -30 °C

Days with Rainfall

≥ 0.2 mm

≥ 5 mm

≥ 10 mm

≥ 25 mm

Days with Snowfall

≥ 0.2 cm

≥ 5 cm

≥ 10 cm

≥ 25 cm

Days with Precipitation

≥ 0.2 mm

≥ 5 mm

≥ 10 mm

≥ 25 mm

Days with Snow Depth

≥ 1 cm

≥ 5 cm

≥ 10 cm

≥ 20 cm

Degree-Days

Degree-Days

Degree-days for a given day represent the number of degrees Celsius that the
mean temperature is above or below a given base. For example, heating
degree-days are the number of degrees below 18 °C.
If the temperature is equal to or greater than 18, then the number of heating
degrees will be zero. Normals represent the average accumulation for a given
month or year.

Values above or below the base of 18 °C are used
primarily to estimate the heating and cooling requirements of buildings
and fuel consumption. A temperature base of 24 °C
is sometimes used as an index of extreme cooling degree-days of as an index
of potential heat stress. Values above 5 °C are
frequently called growing degree-days, and are used in agriculture
as an index of crop growth.

Soil Temperature

Soil Temperature

Soil temperature measurements provide a climatology of soil thermal
characteristics such as the depth of frost penetration into the soil
and the duration that the soil remains frozen. It is of interest to
hydrologists because it affects surface runoff, infiltration and
snowmelt and to agriculturalists because it affects seed germination.

Measurements of soil temperature are made in accordance with the
World Meteorological Organization (WMO) recommendations at
the standard depths of 5, 10, 20, 50, 100, 150 and 300 cm.
They are measured daily as close as possible to 08:00 LST
and again at the shallowest depth at 16:00 LST.

Evaporation

Evaporation

Evaporation refers to the calculated lake evaporation occurring from
a small natural open water-body having negligible heat storage and
very little heat transfer at its bottom and sides. It represents the
water loss from ponds and small reservoirs but not from lakes that
have large heat storage capacities. Lake evaporation is calculated
using the observed daily values of pan evaporative water loss, the
mean temperatures of the water in the pan and of the nearby air, and
the total wind run over the pan.

Lake Evaporation normals for the 1981 to 2010 period were calculated
as means of daily means for a given station. This in effect is a measure of
the rate of evaporation per day rather than a measure of total evaporation
as was calculated in the 1961 to 1990 normals. To make the 1981 to 2010
lake evaporation normal values comparable to previous calculations, multiply
the 1981 to 2010 value by the number of days for a given month to
obtain an equivalent estimate.

Frost and Freezing-Free Period

Frost and Freezing-Free Period

Freezing occurs whenever temperatures fall to 0 °C
or lower. Frost data normals are
based on the occurrence of freezing temperatures as recorded from minimum
thermometers. The "Freezing-free Period" is defined as the number of days
between the last occurrence of frost in spring and first occurrence of frost
in the fall for a given year. For the purpose of these calculations,
"spring" is defined as days on or before
July 15, "fall" is defined as days after July 15 and
freezing or frost occurs on any day where the daily minimum
temperature (Tmin) is observed to be less
than or equal to 0 °C.

"Freezing-free" elements are calculated only for stations where daily
minimum temperature observations are 100% complete from the period of
July 15 to the last occurrence of Tmin less than or equal to
0 °C in "spring", and from July 15 to the first
occurrence of Tmin less than or equal to 0 °C
in "fall". At least one complete period must occur within 1981 to 2010.

Frost normals (Average date of last Spring frost, Average date
of first Fall frost and Average length of Frost-Free period) for
the 1981-2010 period were calculated
as means of the Julian days and represent the last
"spring" frost, first "fall" frost and frost-free length.

Probability statistics are only generated for stations with at
least 10 years of data. These statistics outline the probability
of an event occurring either before or after a specified date.
For example, a date of May 15th given for the
10th percentile of the "Probability of last temperature
in spring of 0 °C or lower
on or after indicated dates",
implies that there is a 10% likelihood that the last spring frost
occurred on either May 15th or later. Similarly a date
of August 15th given for the 10th percentile of the
"Probability of first temperature in fall of 0 °C or
lower on or before indicated dates", implies that there is a 10%
likelihood that the first fall frost occurred on either August
15th or earlier. Finally, a station with 100 days given
for the 10th percentile of the "Probability of frost-free period
equal to or less than indicated period (Days)", implies that there
is a 10% likelihood that the frost-free period for the station is 100
days or less. Calculations for probability of spring freezing at x%,
fall freezing at x% and freezing-free period at x% were completed
using the same methodology. These statistics are calculated for the
entire period of record for a station.

Hourly Data

Hourly Data

Some climate elements are observed on an hourly rather than a daily
basis. For these elements, the "3 and 5" rule for completeness is
inapplicable given the comprehensive volume of data. Instead, to
qualify for inclusion, hourly elements must have at least 90% of all
available hours for a month complete where means or "days with"
statistics are calculated. As with daily elements, where average
totals are calculated, the record required 100% complete data. The
monthly mean was then assigned an annual code following the
completeness requirements outlined in Table 1.

Wind

The calculation of most frequent wind direction has been updated
in the 1981-2010 normals. Most frequent
wind direction is based on the total number of occurrences of each
of 36 possible directions (in 10's of degrees) for each month
converted into one of 8 compass directions. For each of the 8
compass directions the total counts for these 10's of degrees are
added together. The direction with the highest summed amount is the
most frequent wind direction. The most frequent wind direction for
the year is simply deduced as the summed direction with the highest
total occurrence count for all months.
The 8 compass directions are determined from the chart given below.

Wind speed and direction are greatly affected by proximity to the
ground and by the presences of obstacles such as hills, buildings and
trees. It tends to increase in speed and veer with height above
ground. For meteorological purposes, the standard exposure of
anemometer cups is at a height of 10 metres above the ground surface.

Bright Sunshine

Bright Sunshine

Bright sunshine observations are made using the Campbell-Stokes
sunshine recorder. It consists of a glass sphere that is 10 cm in
diameter, mounted concentrically in a portion of a spherical bowl. The
sun's rays are focused by the glass sphere on a card held in position
by a pair of grooves in the bowl. The focused rays scorch the card or
burn a trace right through it. The card size used depends on the
length of the day and is available in three classes corresponding to
the time of the year equinox, summer or winter solstice.

Cards are changed daily so that the duration of sunshine for each
hour of the day can be scaled. It is important to note that the amount
of "bright sunshine" is less than the amount of "visible sunshine"
because the sun's rays are not intense enough to record especially
just after sunrise and towards sunset. The number of tenths of hours
of sunshine are counted, as indicated by the burn on the card, and the
total is recorded.

Humidex

Humidex

Humidex is an index to indicate how hot or humid the weather feels
to the average person. It is derived by combining temperature and
humidity values into one number to reflect the perceived temperature.
For example, a humidex of 40 means that the sensation of heat when the
temperature is 30 degrees and the air is humid feels more or less the
same as when the temperature is 40 degrees and the air is dry.

Dew point is expressed in Kelvins (temperature in K = temperature in
°C + 273.16) and 5417.7530 is a rounded
constant based on the molecular weight of water, latent heat of
evaporation, and the universal gas constant.

Wind Chill

Wind Chill

Wind chill is an index to indicate how cold the weather feels to the
average person. It is derived by combining temperature and wind
velocity values into one number to reflect the perceived temperature.
For example, if the outside temperature is -10 °C and the wind chill is -20, it means that your face will feel
more or less as cold as it would on a calm day when the
temperature is -20 °C.

In the previous normals, wind chill was calculated
when the temperature of the air was ≤ 10 °C and the reported wind speed was
≥ 5 km/h. The first equation listed
below was used for these calculations. In the 1981-2010 normals there are
two Wind Chill formulas used by Environment Canada.
The first equation is used when the temperature of
the air is ≤ 0 °C and the reported
wind speed is ≥ 5 km/h.
The second equation is used when the temperature
of the air is ≤ 0 °C and the reported
wind speed is > 0 km/h but < 5 km/h.

Where W is the wind chill index, based on the Celsius
temperature scale Tair is the air temperature in degrees Celsius (°C), and
V10m is the wind speed at 10 metres (standard anemometer
height), in kilometres per hour (km/h).

Humidity

Humidity

Vapour pressure is the pressure exerted by the water present in an
air parcel. This pressure is one of the partial pressures that make up
the total pressure exerted by an air parcel. The vapour pressure
increases as the amount of water vapour increases.

If an enclosed container of air and liquid water is maintained at a
constant temperature, water molecules escape from the liquid surface
into the air until an equilibrium is reached when no more water will
evaporate (saturation occurs). The air parcel can hold no more water
vapour molecules unless external heating is applied. The pressure
exerted by the water vapour, in this case, is known as the saturation
vapour pressure. The ratio of the actual vapour pressure to the
saturation vapour pressure is another way of defining the relative
humidity of an air mass.

Relative humidity is the ratio of the actual amount of water vapour
present in a given parcel of air to the maximum amount that the parcel
is capable of holding at a given temperature. It is usually expressed
as a percentage. It is derived from either dry bulb and wet bulb
temperatures or, in the case of a Dewcel remote temperature sensing
unit, from dry bulb temperature and dew point values, with the aid of
psychrometric tables.

Relative humidity changes with the air temperature even though the
actual amount of water vapour present in an air parcel may remain
constant. When a parcel of air is heated, without the addition or
removal of water vapour, the relative humidity decreases and
conversely, if the parcel is cooled under the same conditions, the
relative humidity increases.

The closer the dew point temperature is to the dry bulb temperature,
the higher the relative moisture content of the air. At 100% relative
humidity the dew point temperature and the dry bulb temperature are
the same. When the dry bulb/dew point difference is small, some of the
internal water vapour condenses to form liquid water droplets either
as fog or clouds.

Pressure

Pressure

Pressure is the weight of a column of air of unit cross-sectional
area extending from the level of the observing station vertically to
the outer limit of the atmosphere. The standard instrument for the
measurement of atmospheric pressure is the mercury barometer, in which
the air pressure is balanced against the weight of a column of mercury
in a glass tube that contains a vacuum.

Station Pressure (kPa) is the atmospheric pressure in kiloPascal
(kPa) at the station elevation. Atmospheric pressure is the force per
unit area exerted by the atmosphere as a consequence of a mass of air
in a vertical column from the elevation of the observing station to
the top of the atmosphere.

Sea level pressure is the weight of a column of air of unit
cross-sectional area extending from sea level vertically to the outer
limit of the atmosphere. It is directly measured at stations situated
at sea level, but is calculated at other stations by adding to the
station pressure, the equivalent weight of an air column extending
from the station elevation down to sea level. Mean sea level pressure
is computed so that the barometric pressures at stations of different
elevations can be compared at a common level for analysis purposes.

Solar Radiation

Solar Radiation

Solar radiation is the measurement of radiant energy from the sun, on
a horizontal surface. There are several standardized components of
independent measurements. Each component is assigned a different
identifying number referred to as Radiation Fields (RF). The standard
metric unit of radiation measurement is the Mega Joule per square
metre (MJ/m2).

Components measured and used by MSC:

RF1: Global Solar Radiation: the total incoming direct and diffuse
short-wave solar radiation received from the whole dome of the sky on
a horizontal surface.

RF2: Sky Radiation (Diffuse): the portion of the total incoming
short-wave solar radiation received on a horizontal surface that is
shielded from the direct rays of the sun by means of a shade ring.

RF3: Reflected Solar Radiation: the portion of the total incoming
short-wave radiation that has been reflected from the Earth's surface
and diffused by the atmospheric layer between the ground and the point
of observation onto a horizontal surface.

RF4: Net Radiation: the resultant of downward and upward total
(solar, terrestrial surface, and atmospheric) radiation received on a
horizontal surface.

Visibility (km)

Visibility (km)

Visibility in kilometers (km) is the distance at which objects of
suitable size can be seen and identified. Precipitation, fog, haze or
other obstructions such as blowing snow or dust can reduce atmospheric
visibility.

Cloud Amount

Cloud Amount

A cloud in the atmosphere is a visible collection of minute particle
matter, such as water droplets and/or ice crystals, in the air.
Condensation nuclei, such as smoke or dust particles, form a surface
around which water vapour can condense and create clouds.

APPENDIX A

APPENDIX A

Table 2 shows the calculation, period of record and completeness
required for each normal and extreme element.

Table 2: Normals Calculation for the 1981 to 2010 Climate Normals for Canada including element by Group, type of Calculation, period used and completeness required fields